1. Field of the Invention
The present invention relates to a magnetic recording medium such as a magnetic tape or a magnetic disc.
2. Description of the Related Art
As tape-form magnetic recording media for audio, video, and computers, and disc-form magnetic recording media such as flexible discs, a magnetic recording medium has been used in which a magnetic layer having dispersed in a binder a fine ferromagnetic powder such as γ-iron oxide, Co-containing iron oxide, chromium oxide, or a ferromagnetic metal powder is provided on a support. With regard to the support used in the magnetic recording medium, polyethylene terephthalate, polyethylene naphthalate, etc. are generally used. Since these supports are drawn and are highly crystallized, their mechanical strength is high and their solvent resistance is excellent.
The magnetic layer, which is obtained by coating the support with a coating solution having the fine ferromagnetic powder dispersed in the binder, has a high degree of packing of the fine ferromagnetic powder, low elongation at break, and is brittle, and it is therefore easily destroyed by the application of mechanical force and might peel off from the support. In order to prevent this, an undercoat layer is provided on the support so as to make the magnetic layer adhere strongly to the support.
On the other hand, magnetic recording media having a radiation-cured material layer formed using a compound having a functional group that is curable by radiation such as an electron beam, that is, a radiation curable compound, are known (ref. JP-A-57-40747, JP-A-58-146023, JP-A-60-150227, and JP-B-5-57647 (JP-A denotes a Japanese unexamined patent application publication and JP-B denotes a Japanese examined patent application publication)). However, the radiation-cured material layer employing such a radiation curable compound cannot provide sufficient smoothness for the magnetic layer, and adequate electromagnetic conversion characteristics cannot be obtained. Furthermore, since the peel strength of the magnetic layer is not sufficient, when the medium is repeatedly run in a VTR, etc., part of the magnetic layer is peeled off, thus causing faults such as dropouts. Moreover, since the radiation-cured material layer is soft, there is the problem that it often sticks to a path roller, etc. during a coating step, etc.